This invention relates to magnetic printing heads, and in particular to a method of manufacturing a high resolution transverse magnetic printing head using electrodeposition to form a comb-like, magnetically permeable structure.
Magnetic printing is a rapid and silent system for producing images of both alpha-numeric and pictorial data. Briefly, magnetic printing involves the transfer of dry magnetic ink from a ferromagnetic recording medium to paper. Magnetic ink is selectively attracted to portions of the magnetic recording medium which have been magnetized with the aid of a recording head which typically possesses a comb-like magnetically permeable structure. Adjacent teeth of the comb-like structure define gaps which facilitate the concentration of magnetic flux at the tips of the teeth. In a transverse printing head, teeth tips are positioned in close proximity to the magnetic recording medium which is conventionally moved past the recording head in a direction perpendicular to the direction of magnetic flux lines between the tips of adjacent teeth of the comb-like structure. Typically, a plurality of current-carrying conductors pass through each gap in the comb-like structure. Current magnitude in the conductors controls the level of magnetic flux at the tips of the teeth. When sufficient current is passed through selected conductors, the increased flux is sufficient to magnetize selected portions of the recording medium which thereafter attract magnetic ink as the medium passes a magnetic ink dispensing brush assembly. In this manner, the latent magnetic image impressed on the recording medium by the recording head is made visible. The inked recording medium is then, typically, passed between heated rollers having a paper medium disposed therebetween for receiving the magnetic ink from the recording medium. The magnetic recording medium is magnetically erased prior to recording new information thereon. A detailed description of magnetic printing and magnetic printing heads is found in U.S. Pat. No. 4,097,871, issued June 27, 1978 to Berkowitz et al and assigned to the same assignee as the present invention, said patent being incorporated herein by reference.
The resulting printed image quality is directly related to the magnetic printing head resolution which is, in turn, directly related to the spacing between adjacent teeth of the magnetic comb-like structure. At print resolution of approximately 120 gaps or dots per inch, the spacing between adjacent comb teeth and adjacent conductors passing between the teeth is approximately 5 mils. Due to such small tolerances, it is often difficult to insert a conventional comb into the substrate without breaking the delicate conductors or bending the comb teeth. Moreover, if even higher print resolution, such as 200 dots per inch, is desired it does not appear possible to employ conventional comb-like structures.